1. Field of the Invention
This invention relates to safety systems for automatic transmission vehicles and more particularly to a system whose primary function is to warn a driver when he has stopped his vehicle but failed to place the shift lever in park, where "park" means "latched park" so that the vehicle is properly restrained. The system includes subsidiary safety features which will become apparent as the description proceeds.
2. Background of the Invention
The patent to Mochida, U.S. Pat. No. 4,482,885, and applicant's own U.S. Pat. Nos. 5,015,991, 5,581,233, and 5,760,683 are representative of systems which sound an alarm when a driver prepares to leave a vehicle with the transmission selector lever not in park.
The prior art fails to assure that the vehicle park system linkage has moved the parking gear locking pawl into the latched position when the shift lever is in the park position. As us ed herein, the park system comprises three parts--the shift lever, the shift linkage, and the park mechanism. The shift linkage extends between the shift lever and the shaft which pass through the wall of the transmission. That shaft connects the shift linkage to the park mechanism. The park mechanism is inside the transmission. The prior art discloses use of a switch, located at the transmission end of the shift linkage, that is moved to the open position to prevent the activation of an alarm when the shift lever is in park and the shift linkage is apparently not broken or maladjusted. However, the prior art fails to teach or suggest locating such a switch in a position which completely assures that the locking pawl is in its latched position when that switch opens upon placing the shift lever in the park position. The present invention overcomes this deficiency in the prior art.
One object, therefore, of the invention is to provide a system for automatic transmission vehicles whose function is to sound alarms calling attention to the oversight of failing to place the shift lever in park or to the vehicle shift linkage and park mechanism derangement which results in the failure of the locking pawl to completely engage within the groove between a pair of teeth on the parking gear.
Another object of the invention is to provide an improved alarm system whose function is to sound alarms calling attention to the oversight of failing to place the shift lever in park or to vehicle shift linkage and park mechanism derangement which includes a normally closed park system switch which is opened by operation of a portion of the park mechanism, for example, the parking gear locking pawl or the end of the park apply rod as the locking pawl moves into its latched position when the shift lever is placed in park.
Another object is to provide a seat switch circuit that causes the locking pawl to engage the parking gear if the driver leaves his normal driving position without placing the shift lever in park.